diff --git a/gdb/corelow.c b/gdb/corelow.c
index 954607134f4..216b4e70066 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -1239,6 +1239,13 @@ core_target_open (const char *arg, int from_tty)
 void
 core_target::detach (inferior *inf, int from_tty)
 {
+  /* The core BFD is set when the core_target is created and attached to
+     the inferior.  It is only cleared during detach or close.  After
+     detaching the core target will be closed and deleted, so detach can
+     never be called twice.  What this means is that detach will never be
+     called without the core BFD being set.  */
+  gdb_assert (this->core_bfd () != nullptr);
+
   /* Get rid of the core.  Don't rely on core_target::close doing it,
      because target_detach may be called with core_target's refcount > 1,
      meaning core_target::close may not be called yet by the
@@ -1250,9 +1257,7 @@ core_target::detach (inferior *inf, int from_tty)
      implementation deletes 'this'.  */
   inf->unpush_target (this);
 
-  /* Clear the register cache and the frame cache.  */
-  registers_changed ();
-  reinit_frame_cache ();
+  /* Inform the user.  */
   maybe_say_no_core_file_now (from_tty);
 }